The invention relates to an optical unit for synchronizing clock signals. In systems operating with high frequency signals, i.e. signals having a frequency of more than 10 GHz, there is the problem that the current electronic components are not fast enough and are thus not satisfactory. 10 GHz may be considered as an electronic barrier. Moreover, these systems also comprise semiconductor lasers in many cases, which can generally be modulated to frequencies of 10-15 GHz maximum. Applications in which high-frequency signals are desired and will also play an important role in the future are, for example, satellite transmission, optical telecommunication and mobile telephony.
The invention also relates to a transmission system having high-frequency carrier waves, provided with such an optical unit.